Orthokeratology and bi-focal contact lens

ABSTRACT

A contact lens is fitted to a cornea of a patient&#39;s eye to gradually alter the patient&#39;s cornea during continued wear to reshape the cornea to reduce the hyperopia and/or presbyopia condition. The contact lens has a plurality of zones that includes one or two optical zones, a plateau zone, a fitting zone, an alignment zone and a peripheral zone. The one or more optical zones are utilized to redistribute cornea tissue to cause the cornea to have a steepened central portion surrounded by a flat mid-peripheral ring The plateau zone helps steepening the central cornea by two ways: a positive molding effect of pushing the cornea tissue inward to pile up and a negative molding effect to flatten the mid-peripheral cornea for enhancing.

RELATED APPLICATION

[0001] The present invention is a continuation-in-part of a pendingapplication, Ser. No. 09/715,964, filed Nov. 17, 2000, by the inventorhereof, entitled ORTHOKERATOLOGY CONTACT LENS, whose disclosure isincorporated by this reference as though set forth fully herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to contact lenses that are used intreating hyperopia and presbyopia, and more particularly, to contactlenses that are shaped to provide gradual altering of the patient'scornea during continued wear to reshape the cornea to reduce thehyperopic and presbyopic condition.

[0004] 2. Description of the Related Art

[0005] Many people experience difficulties with their vision due to anumber of possible conditions. The most common vision problem is acondition known as myopia or nearsightedness. Myopia is a commoncondition where an eye cannot focus on far-away objects because thecornea of the eye is curved too steeply (i.e., where the radius ofcurvature of the cornea is smaller than normal) to provide adequatefocusing at the retina of the eye. Another condition is known ashyperopia or farsightedness. With hyperopia, the eye cannot focus onboth far and near objects because the curvature of the cornea of the eyeis too flat (i.e., where the radius of curvature of the cornea is largerthan normal)to provide adequate focusing at the retina of the eye.Hyperopia is common among young children. Severe hyperopia will inducelazy eye or amblyopia in childhood. Mild or moderate hyperopia istolerable and insidious in young ages but will cause reading problems inolder age. Another common problem is astigmatism, where unequalcurvature of one or more refractive surfaces of the cornea preventslight rays from focusing clearly at one point on the retina, resultingin blurred vision. Presbyopia is the most common vision problem inadults 40 years and older. It does not matter whether they areemmetropic, myopic or hyperopic in far vision, the middleaged populationover 40 years old will begin to experience difficulty in focusing onclose objects, due to the loss of flexibility of the eye's crystallinelens. Presbyopia may occur and complicate other refractive problems suchas hyperopia, myopia or astigmatism.

[0006] Hyperopia and presbyopia are both conditions for which noentirely suitable permanent treatment has been developed. Theconventional way is to wear a pair of heavy convex glasses. One approachto correcting hyperopia is through laser surgical reshaping of thecornea. However, such surgical procedures have not been entirely safeand there have been less favorable vision outcome for the hyperopiasurgery than that of myopia surgery.

[0007] Another approach to treating some or all of these conditions isto alter the corneal shape by wearing contact lenses which are designedto continually exert pressure on selected locations of the cornea togradually force or mold the cornea into the desired normal cornealcurvature. A retainer lens is then worn on a part-time basis to preventthe cornea from returning to its previously deformed shape. This methodof treatment is commonly referred to as orthokeratology (referred toherein as “ortho-k”). The success of any treatment by ortho-k isdependent upon the shape and structure of the contact lens. For example,conventional contact lenses with a longer central radius of curvaturethan the central radius of the cornea are known to change the shape ofthe cornea by compressing the surface at its apex. This reshaped corneahas a lengthened radius of curvature in its central zone, which servesto improve myopia. Although it has been well known to treat myopia usingmodem Ortho-K lenses to reshape the cornea, treating hyperopia orpresbyopia using Ortho-K lenses has been met with uncertain outcome andresults.

[0008] Ortho-k has been performed in some form or another since theearly 1970s. There are three factors that impact the effectiveness anddesirability of ortho-k procedures and lenses. The first factor is thetime needed to achieve a desired visual correction. Unfortunately, thetime needed to achieve a desired visual correction using conventionalortho-k techniques and lenses has been a serious problem, since it willtake several months, or even years, for small amount of hyperopia to bereduced. The second factor is the amount of hyperopia that can becorrected using ortho-k. Conventional ortho-k techniques and lenses werelimited to a reduction of no more than about one diopter of hyperopia.The third factor is the amount of time that the correction would “hold”before degrading (known as the “maintenance period”). Conventionalortho-k techniques and lenses provide variable length for themaintenance period. To prolong this maintenance period, a patient wouldhave to wear a retainer lens.

[0009] Some patients have been fitted with a series of progressivelysteeper regular RGP lenses to treat hyperopia. The lens diameter wassmall (7-8 mm) and the base curve steeper than the central corneacurvature. Lenses would need to be replaced upon the showing of someeffect, while the results are usually minimal and unpredictable. Thelenses sometimes became tightened to cause adverse effect.

[0010] U.S. Pat. No. 5,963,297 to Reim and U.S. Pat. Nos. 5,349,395,4,952,045, 5,191,365, 6,010,219 to Stoyan disclose Ortho-k lens designsfor myopia reduction. There has been no lens specifically designed forincreasing the curvature power of the cornea for hyperopia reduction.Orthokeratology for the presbyopia has never been addressed or mentionedbefore, largely because it was thought that no lens could mold a corneainto dual shapes for clearing up near, as well as far, visionsimultaneously. The conventional way to treat a myopic, and yetpresbyopic, person by Ortho-k is either to sacrifice the far vision ofboth eyes (under-corrected) or to sacrifice monocular far vision(Mono-vision). Both ways make it hard to be accepted by most of thepatients.

[0011] Notwithstanding the improvements provided by modemOrthokeratology for myopia, there remains a need for a contact lens thatcan be used for effective ortho-k of hyperopia and/or presbyopia.

SUMMARY OF THE INVENTION

[0012] It is an object of the present invention to provide an ortho-kcontact lens that provides effective reduction of hyperopia and/orpresbyopia.

[0013] It is another object of the present invention to provide anortho-k contact lens that provides a shorter correction time.

[0014] It is yet another object of the present invention to provide anortho-k contact lens that provides a longer maintenance period.

[0015] The objects of the present invention may be achieved by providingan apparatus and method for correcting a hyperopia and/or presbyopiacondition in a patient's eye. In accordance with a method of the presentinvention, a contact lens is fitted to a cornea of a patient's eye, thecontact lens having a plurality of zones that includes a optical zone, aPlateau zone, a fitting zone, an Alignment zone and the peripheral zone.The Plateau zone is carefully created to flatten the mid-peripheralcornea curvature to cause the cornea to have a flattened mid-peripheralportion surrounding the central steeper cornea zone. The flattermid-peripheral plateau zone works together with the steeper optical zoneto enhance the steepening of the central cornea to reduce hyperopia. Theconcept of “flattening the mid-peripheral cornea to enhance thesteepening of the central cornea for effective hyperopia reduction” istotally different from that of the conventional method by “squeezing thecornea tissue inward and piling up to steepen the central cornea forhyperopia reduction”. We define the new concepts to be a “dual molding”for hyperopia and/or presbyopia reduction.

[0016] In accordance with an apparatus of the present invention, acontact lens is provided having a base curve portion of the lens, aplateau curve portion of the lens circumscribing and coupled to the basecurve portion, a fitting curve portion of the lens circumscribing andcoupled to the plateau curve portion, and an alignment curve portion ofthe lens circumscribing and coupled to the fitting curve portion, and aperipheral curve portion of the lens circumscribing and coupled to thealignment curve portion.

[0017] The goal of this type of lenses is to mold the cornea into ashape of central steepening just like a hummock on top of a plateau. Theoverall diameter of the central optical zone could be varied or dividedfor different purposes of correcting hyperopia or presbyopia.

[0018] For treating the hyperopic person, the base curve shouldpreferably be steeper than the central cornea curvature. The opticalzone should be wide enough for better far vision. It is also preferredto keep the plateau zone as narrow as possible to prevent it frominducing ghost imaging due to the flattened mid-peripheral area.

[0019] For treating the presbyopic person, the optical zone should bedivided into two portions. The central zone should be designed to bevery small for the purpose of near vision to prevent it from hinderingthe far vision. The outer optical zone then should be much wider to moldthe juxta-central cornea area into a flatter zone to clear up far vision(reducing myopia, hyperopia, or astigmatism if any).

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is a side schematic outline view of an ortho-k contact lensaccording to the present invention in use with a cornea of a patient'seye.

[0021]FIG. 2 is a front planar view of the ortho-k contact lensaccording to one embodiment of the present invention for hyperopiacorrection.

[0022]FIG. 3 is a side sectional view of the ortho-k contact lens ofFIG. 2.

[0023]FIG. 4 is a front planar view of the ortho-k contact lensaccording to another embodiment of the present invention for presbyopiacorrection in a myopic person.

[0024]FIG. 5 is a side sectional view of the ortho-k contact lens ofFIG. 4.

[0025]FIG. 6 is a front planar view of the ortho-k contact lensaccording to one embodiment of the present invention for presbyopiacorrection in a hyperopic person.

[0026]FIG. 7 is a side sectional view of the ortho-k contact lens ofFIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] The following detailed description is of the best presentlycontemplated modes of carrying out the invention. This description isnot to be taken in a limiting sense, but is made merely for the purposeof illustrating general principles of embodiments of the invention. Thescope of the invention is best defined by the appended claims.

[0028] FIGS. 1-3 illustrate an ortho-k contact lens 10 according to oneembodiment of the present invention. As shown in FIG. 1, the contactlens 10 is a dual geometric contact lens that is adapted to be worn overthe cornea 12 of a patient's eye 14. The contact lens 10 has fivecorrection zones, listed from the center of the lens 10 to the outerperiphery: an optical zone 20, a plateau zone 22, a fitting zone 24, analignment zone 26, and a peripheral zone 28.

[0029] Optical Zone

[0030] Referring to FIGS. 2 and 3, the optical zone 20 has a curvaturethat is defined by the base curve 30. The optical zone 20 forms asuitable space for molding tissue to a region substantially centered atthe apical center of the cornea 12, and is responsible for thecorrective steepening or increasing in the radius of curvature of thecentral cornea during treatment. The radius of curvature of the basecurve 30 is smaller than a measured curvature of a central portion ofthe cornea 12 for treatment of hyperopia, thus creating a centraltenting up area 32. The tent-up area 32 provides a suitable space forpiling the cornea tissue up during vision correction.

[0031] The optical zone in the invention may be divided into twoportions for the treatment of presbyopia coupled with hyperopia. A tinyinner additive optical curve 30 b defined by inner additive optical zone20 b is steeper (shorter radii) than the consecutive outer base curve 31b by 1-4 Diopters. The outer base curve 31 b defined by the outeroptical zone 21 b is steeper (shorter radii) than the central curvatureof the cornea 12 by 1-15 diopters. The tented-up spacing under the outeroptical zone 21 b causes the cornea molding to form a steeperjuxta-central portion of the cornea 12 for correcting hyperopia, and theeven steeper inner optical zone 20 b causes the formation of evensteeper curvature of the central portion of the cornea 12 for correctingpresbyopia. The inner optical zone 20 b is preferably kept small enoughto prevent it from hindering the far vision and the size is usually from0.5 to 1.5 mm. As can be appreciated by those skilled in the art, thepupil of human eyes will constrict for near reading (so called “nearreflex”) and dilate when looking into the distance. Since the tinycentral blurred image will be neglected when looking into far distance,we can create a tiny (0.1-1.5 mm) steeper inner optical zone 20 a, 20 bcoupled with a wider (1.5-4.0 mm) and flatter outer optical zone 21 a,21 b to treat the far and near vision simultaneously in one lens.

[0032] The steeper inner optical zone 20 a of FIG. 6 can also beincorporated into a single reverse geometric Ortho-K lens to treatcoexisting presbyopia and myopia simultaneously. In this situation, theinner base curve 30 a, defining the inner optical zone 20 a, is made 1-4diopters (hereinafter “D”) steeper than the outer base curve 31 a,defining the outer optical zone 21 a, to mold the central portion of thecornea 12 into a steeper curvature for reading. The outer optical zone21 a and outer base curve 31 a is determined according to the principleof optical zone/curvature of the reverse geometric ortho-K lenses forproper myopia reduction. The incorporated inner optical zone 20 a has aninner base curvature 30 a that is 1-4 D steeper (shorter radius) thanthe consecutive outer base curve 31 a of outer optical zone 21 a. Theinner additive base curve 30 a is not necessarily steeper (shorterradius), but is preferably flatter (longer radius) than the curvature ofthe central portion of the cornea 12, except when the myopic power ismild and numerically smaller than that of the presbyopic additive powerwhich in turn could be same as, or slightly steeper (shorter radii)than, the curvature of the central portion of the cornea 12. The outerbase curve 31 a, functioning like the central optical zone/base curve ofa reverse geometric Ortho-K lens for myopia reduction, is flatter(larger radius) than the central portion of the cornea 12 by 1-30 D, andis designed to compress the juxta-central portion of the cornea 12 forproper myopia reduction.

[0033] There could be a substitution for dividing the optical zones forpresbyopia reduction, by creating an aspheric base curve with positiveeccentricity (e-value), so that the curvature of the inner portion ofbase curve 30 will be substantially steeper than that of the outerportion of the base curve 30. The curvatures flatten (elongate)continuously from the lens center to the edge of optical zone 20 due tothe eccentricity (e-value). That will then mold the cornea into a shapeof a steeper central portion for the near vision and a flatterjuxtacentral portion for the far vision.

[0034] In one embodiment of the present invention, the diameter of theoptical zone 20 ranges from 3 mm to 8 mm, and the inner optical zone 20a, 20 b ranges from 0.5 mm to 1.5 mm, the outer optical zone 21 a, 21 branges from 1.0 mm to 4.0 mm, and the radii of the curvature for thebase curve 30 and the inner base curve 30 a, 30 b and the outer basecurve 31 a, 31 b ranges from 15.0 mm to 5.0 mm.

[0035] Plateau Zone 22

[0036] Referring to FIGS. 2, 3, 4 and 5, the Plateau zone 22 has aradius of curvature defined by a predefined plateau curve 34, which islonger (i.e., flatter) than the radius of curvature associated with thebase curve 30 or outer base curve 30 a. On the lens 10 a for thereduction of myopia coupled with presbyopia, the flatter plateau zone inlens 10 a merges with the flatter outer optical zone 31 a and can belooked upon as a continuous and gradual-flattening curve with positivee-value.

[0037] This longer radius of curvature of the plateau zone 22 defines aplateau curvature 34 that is flatter (longer radius) than the measuredcurvature of the central portion of the cornea 12 and the measuredcurvature of the portion of the cornea 12 circumscribing the centralportion of the cornea 12. As mentioned above, the plateau zone 22functions as a primary compression force to the mid-peripheral cornearegion substantially surrounding the apical central cornea between theinner and outer optical zones 20, 21 a, 21 b and the fitting zone 24.

[0038] The plateau zone 22 is preferably kept as narrow as possible, sothat it can function as a compression zone for mid-peripheral corneaflattening. The flattened mid-peripheral cornea will in turn enhance thecentral cornea 12 for further steepening. The molding technique is named“dual molding” which includes a positive molding for central corneasteepening and a negative molding for mid-peripheral cornea flattening.The lens design can also be named a “dual geometric lens” which includea positive geometric zone and a negative geometric zone for the steeperoptical zone and flatter plateau zone respectively. A narrow flattenedmid-peripheral cornea area coupled with a large steepened central andjuxta-central cornea area will prevent the person from being bothered byghost image in far vision.

[0039] As can now be appreciated, the plateau zone 22 performs threeprimary functions. First, the provision of the plateau zone 22 allows aneffective compression on mid-peripheral cornea to push the cornea tissueinward, which in turn steepens the cornea curvature of the centralportion of the cornea 12. This represents the positive molding componentof the “dual molding”. The compression force exerted by the flatterplateau zone 22 on mid-peripheral cornea portion will be far moreeffective for tissue molding than the compression force by traditionalmethod of a series of steeper regular RGP. The compression force by asteep fit regular RGP is exerted on more peripheral cornea and is moretangential to the compressed area, so that most of the molded tissuewill pile up at mid-peripheral area instead of the central area to causean adverse effect.

[0040] Second, the plateau zone 22 functions as a compression zone forthe effective flattening of the mid-peripheral area surrounding thesteepened central cornea area 12. Forming a plateau shape on themid-peripheral area of the cornea 12 by the compression force of plateauzone 22 will in turn enhance the steepening effect of the centralcornea. The negative molding component of “dual molding” flattens themid-peripheral cornea 12 and effectively enhances the positive moldingof steepening the central and juxta-central portion of the cornea 12.The flatter plateau zone will also prevent the cornea tissue, which issqueezed inward by the alignment zone 26 (described later), from pilingup at the mid-peripheral area. Piling up of the cornea tissue on themid-peripheral area would have adversely flattened the central corneacurvature and increased the hyperopia, instead of reducing it. This isone of the problems that conventional orthokeratology frequentlyencountered.

[0041] Third, the flat plateau curve 34 of the plateau zone 22 reservesmore room for the vertical height of the fitting zone 24 so that thefitting curve 36 can be fitted much steeper than the plateau curve 34.This allows the fitting curve 36 to form a space for proper tearcirculation and a room for tissue molding before connecting to thealignment zone 26 (described later).

[0042] In one embodiment of the present invention, the diameter of theplateau zone 22 ranges from 0. 1 mm to 2.0 mm. The radius of curvaturefor the plateau curve 34 is flatter (longer radius) than the centralbase curve 30 or outer base curve 31 b by 3-30 diopters, and is usuallybetween 8-25 diopters. In lens 10 a, the plateau zone 22 and plateaucurve 34 merges with the outer optical zone 21 a and outer base curve 31a, respectively.

[0043] Although the present invention illustrates the provision of oneplateau curve 34, it is also possible to provide the contact lens 10with two or more plateau zones and curves as well as substitute the zonewith an aspheric curve of a positive e value, or even merge with zone 21a or zone 21 b to form a continuously flatter curvature next to theinner optical zone 20 a or 20 b.

[0044] Fitting Zone 24

[0045] Referring to FIGS. 2 and 3, the fitting zone 24 of lens 10 has aradius of curvature defined by a fitting curve 36 with the radius ofcurvature being less than (i.e., shorter than) the radius of curvatureassociated with the plateau curves 34. Since the plateau zone and curvein lens 10 a (shown in FIGS. 4 and 5) merge with the outer optical zone21 a and outer base curve 31 a, the plateau curve 34 in lens 10 a canthen be looked upon as having the same definition of outer optical zone21 a and outer base curve 31 a for lens 10 a shown in FIGS. 4 and 5.This shorter radius of curvature of the fitting zone 24 yields a fittingcurvature 36 that is much steeper than the plateau curve 34. Althoughthe fitting curve 36 is much steeper (smaller radius) than the plateaucurves 34, the curvature 36 may not necessarily be steeper than themeasured curvature of the central portion of the cornea 12, or themeasured curvature of the portion of the cornea 12 circumscribing thecentral portion of the cornea 12.

[0046] The fitting zone 24 acts as a transition region between theplateau zone(s) 22 and the alignment zone 26. The fitting zone 24 bringsthe posterior surface of the contact lens 10 to a bearing relationshipon the mid-peripheral portion of the cornea 12 under the plateau zone22, and provides compression force on the plateau zone 22, therebycompressing the mid-peripheral portion of the cornea 12, for dualmolding of the cornea 12. In one embodiment of the present invention,the width of the fitting zone 24 ranges from 0.1 mm to 2.0 mm, theradius of curvature for the fitting curve 36 is 5-30 diopters steeperthan the plateau curve 34, and is 15 diopters flatter to 15 diopterssteeper than the base curve.

[0047] At this time, it should be noted that a lens can be calculatedfrom the view point of saggital depth. A saggital depth calculationtranslates the component curvatures and each width for a lens into asimple factor known as the saggital depth. A saggital depth will bemeasured from the center of a lens to the denoted width, and will alsodefine the slope of an area on a lens. In other words, the angles A1,A2, A3 and A4 illustrated in FIG. 3 can be calculated as the “saggitaldepth/zone width” and can be considered to be a slope ratio, which canbe defined as the vertical height/zone width. Since a dual geometriclens has multiple curvatures, we have to calculate the vertical heightof each zone and add them up. Here, the summation of (i) vertical heightof the optical zone 20, (ii) the vertical height of the plateau zone 22, and (iii) the vertical height of the fitting zone 24 should be equalto the height of the original cornea with the same zone width (i.e., the3 total zones) plus 10 microns (this additional 10 microns is anallowance made to prevent the lens 10 from bearing on the cornea 12).This is the underlying principle of saggital depth calculation. A moredetailed explanation of saggital depth calculation is provided inADVANCED CL FITTING, PART SEVEN, TRENDS IN MODERN ORTHOKERATOLOGY,Optician, No. 5645, Vol. 215, Apr. 3, 1996, pages 20-24, whose entiredisclosure is incorporated by this reference as though fully set forthherein.

[0048] Alignment Zone 26

[0049] Referring to FIGS. 2 and 3, the alignment zone 26 is designed toprovide and maintain centration of the lens 10 by having a radius ofcurvature that is either the same as, or slightly longer than thecentral curvature of the cornea 12 (i.e., to match the peripheralcornea). A predefined alignment curve 38 defines the curvature of thealignment zone 26, which is almost the same as the measured curvature ofthe portion of the cornea 12 circumscribing the central portion of thecornea 12.

[0050] The alignment zone 26 creates a large bearing area 40 in a regioncorresponding with the portion of the cornea 12 where a centering forceis created that maintains the optical zone 20 substantially at theapical center of the cornea 12. The alignment zone 26 further produces asecondary compressive force in the large bearing area 40 that cooperateswith the primary compressive force from the plateau curve to flatten themid-peripheral portion of the cornea 12 contributes to the negativemolding component of the dual molding for hyperopia and/or presbyopiareduction during vision correction.

[0051] The alignment curve 38 is determined by mean K (also known asKM). In other words:

[0052] a. (Vertical KM+Horizontal KM)/2.

[0053] The central mean K in turn will be recalculated to estimate themid-peripheral radius of curvature according to the eccentricity(e-value) of a cornea to match the point that the alignment zone 26contacts the cornea 12. This calculation method enjoys two benefits overknown methods. First, this calculation method can be used for both toric(astigmatic) or non-toric corneas. Corneas with the same horizontalcentral KM do not mean they should be fitted with the same ortho-k lens.The vertical curvature could be different (astigmatic or toric cornea),the e-value could also be different, and they should be considered asdifferent corneas. Second, by considering the e-value of a normalcornea, the peripheral attachment of the alignment zone 26 will beimproved.

[0054] The associated alignment curve 38 creates a bearing zone over alarge surface area of the cornea 12, which is helpful in aligning thelens 10 at the apex of the cornea 12. In one embodiment of the presentinvention, the width of the alignment zone 26 ranges from 0.1 mm to 5.0mm (depending on the fitting characteristics desired and the particularshape factors of the cornea 12), the radius of curvature for thealignment curve 38 is 1-30 diopters steeper than the plateau curve 34,and the alignment curve 38 is also about 1-25 diopters less steep (i.e.,flatter) than the fitting curve 36 .

[0055] Alternatively, the alignment zone 26 can be segmented intomultiple curves and any combination of any shapes or curves, as long assufficient bearing area is maintained.

[0056] Peripheral Zone 28

[0057] The peripheral zone 28 is designed with a radius of curvaturelonger than that of the cornea 12, yielding a curvature less than ameasured curvature of a portion of the cornea 12 circumscribing thecentral portion of the cornea 12 that corresponds to the alignment zone26. The peripheral zone 28 has its surface contour defined by apredefined peripheral curve 42 which has a curvature that nearlyparallels the portion of the cornea 12 underneath it, but is flatterthan the cornea 12. The peripheral zone 28 promotes tear flow under thecontact lens 10 by taking advantage of a tear pumping action createdwhen the individual blinks the eyelid. This tear flow allows constantlubrication and oxygenation of the lens-comea interface and results in amore comfortable and wearable lens 10.

[0058] Additionally, the peripheral zone 28 is designed to create aslight edge lift which allows easy contact lens removal from the cornea12. In one embodiment of the present invention, the width of theperipheral zone 28 ranges from 0.1 mm to 2.0 mm, the radius of curvaturefor the peripheral curve 42 is 0-15 diopters greater (flatter) than theplateau curve 34, and is also about 1-35 diopters greater (longer radii)than the fitting curve 36, or the alignment curve 38. The peripheralcurvature should be carefully calculated according to the aforementionedsaggital theory to achieve an edge lift of 100-120 microns. Anoverly-large edge lift may induce a reverse suction force to create airbubbles under the lens 10, while an overly-small edge lift may reducetear circulation and cause lens seal-off.

[0059] The different radii used to define the base curve 30, the plateaucurve 34, the fitting curve 36, the alignment curve 38 and theperipheral curve 42 are calculated after careful examination of thepatient's eye and the associated ocular tissue. The corneal curvaturemust be measured, the proper contact lens power defined, and theanticipated physiological response to the contact lens 10 must bedetermined. An individual skilled in the examination techniques of theocular system is typically capable of performing these tasks.

[0060] As explained above, the provision of one or more plateau zones 22offers dual molding force to facilitate the steepening of the centralportion of the cornea 12 for hyperopia and/or presbyopia correction. Theinvention of a tiny and steeper inner optical zone 30 a, 30 b open up anew era of correcting dual refraction errors of presbyopia coupled withhyperopia, or presbyopia coupled with myopia simultaneously in one lens.The present invention enables treatment of dual refractive problems inone lens by dual molding force from a dual geometric lens. A typicaldual geometric lens will have consecutive curvatures featuringinterlaced steep-flat-steep-flat curvatures from the central portionoutward. Of course, there can be additional zones or eccentricity(e-value) incorporated into the basic components as previouslymentioned.

[0061] For example, the contact lens 10 of the present invention canachieve a reduction of hyperopia up to 2.0-10.0 diopters with a shorterwearing time (e.g., 6-10 hours a day for initial wearing, and 4-8 hoursa day to maintain) and longer maintenance period (e.g., 1-7 days afterthe lens 10 is removed).

EXAMPLE 1

[0062] A contact lens having the following dimensions was provided for aAA0786 patient:

[0063] <Right Eye>

[0064] KM: 43.375 D(7.78 mm)@H, 44.5 D(7.85 mm)@V

[0065] Refraction: +2.00-0.75@130(hyperopia +2.00D astigmatism 0.75Daxis 130)

[0066] optical zone 20: width 4.0 mm, radius of curvature 7.25 mm

[0067] plateau zone 22: width 1.1 mm, radius of curvature 9.79 mm

[0068] fitting zone 24: width 0.5 mm, radius of curvature 6.57 mm

[0069] alignment zone 26: width 1.2 mm, radius of curvature 7.85 mm

[0070] peripheral zone 28: width 0.4 mm, radius of curvature 11.30 mm

[0071] <Left Eye>

[0072] KM: 43.375 D(7.78 mm)@H,44.5 D(7.85 mm)@V

[0073] Refraction: +3.00-1.00@40 (hyperopia +3.00D and astigmatism 1.00Daxis 40 degree)

[0074] optical zone 20: width 4.0 mm, radius of curvature 7.16 mm

[0075] plateau zone 22: width 1.1 mm, radius of curvature 9.85 mm

[0076] fitting zone 24: width 0.5 mm, radius of curvature 6.59 mm

[0077] alignment zone 26: width 1.2 mm, radius of curvature 7.85 mm

[0078] peripheral zone 28: width 0.4 mm, radius of curvature 11.30 mm

[0079] The contact lenses were worn by the patient for 7 day, at 7-8hours a day.

[0080] After this correction period, the patient experienced a hyperopiaand astigmatism reduction to zero power. This is equivalent to ahyperopia reduction of +1.75 D for the right eye and +2.50D (sphericalequivalent) for the left eye. The maintenance period (of nearly zeropower) lasted for all awakening hours with a 5-7 hour maintenance nightwearing. The topography of the cornea is well-centered and has adefinite boundary of a hummock-on-plateau shape to support an efficientreduction in hyperopia. This case has been followed for ths with no sideeffects.

EXAMPLE 2

[0081] A contact lens having the following dimensions was provided for aAA0751 patient:

[0082] <Right Eye>

[0083] KM: 42.25(7.99 mm), 43.125(7.83 mm)

[0084] Refraction: −3.00-0.50@90(myopia −3.00D astigmatism 0.50D axis 90degree)

[0085] With Presbyopic Near addition of +1.50D, corrected to 20/20 at 40cm

[0086] (Since the right eye is the sighting eye for far, we designed areverse geometric lens for right eye to correct her myopia only)

[0087] optical zone: width 5.6 mm, radius of curvature 8.89 mm

[0088] fitting zone : width 0.8 mm, radius of curvature 7.04 mm

[0089] alignment zone: width 1.5 mm, radius of curvature 8.03 mm

[0090] peripheral zone: width 0.4 mm, radius of curvature 11.80 mm

[0091] <Left Eye>

[0092] KM: 42.00 D(8.04 mm)), 42.65 D(7.91 mm)

[0093] Refraction: −3.00-0.50@75(myopia −3.00D and astigmatism 0.50Daxis 40 degree)

[0094] With presbyopic near addition of +1.50D, corrected to 20/20 at 40cm

[0095] (We corrected her left eye for myopia as well as presbyopiasimultaneously)

[0096] inner optical zone 20 a: width 1.0 mm, radius of curvature 8.50mm

[0097] outer optical zone 21 a: width 2.50 mm, radius of curvature 8.83mm

[0098] plateau zone 22: none (merged with outer optical zone 21 a)

[0099] fitting zone 24: width 0.6 mm, radius of curvature 6.85 mm

[0100] alignment zone 26: width 1.5 mm, radius of curvature 8.07 mm

[0101] peripheral zone 28: width 0.4 mm, radius of curvature 11.90 mm

[0102] The contact lenses were worn by the patient for 7 day, at 7-8hours a day.

[0103] After this correction period, the patient experienced a myopiaand astigmatism reduction to zero power for both eyes. The far visionwas 20/20 on right eye and 20/25+ on left eye. The near vision was 20/40on right eye but was 20/20 on left eye. The patient enjoyed thesimultaneous improvement of far and near visions. There are two reasonsfor correcting monocular presbyopia on left eye instead of on both eyes,first is for comparing the far and near vision between both eyes fordemonstration, second is to preserve a clearer far vision for heroccupational requirement. We learn from this case that the influence onfar vision by the incorporation of tiny inner central optical zone 21 ais minimal (one line decrease only). On the other hand, the quality ofthe near vision will be much improved (from 20/40 on right to 20/20 onleft eye) by the incorporation of inner optical zone 21 a. There shouldhave been no problem fitting both eyes with dual geometric lenses if therequirement for far vision was not so critical. Otherwise we shouldcorrect the non dominant eye(left eye in this case) for reading andmaintain a better far vision for the dominant sighing eye (right eye inthis case).

[0104] The maintenance period (of nearly zero power) lasted for allawakening hours with a 5-7 hour maintenance night wearing. Thetopography of the cornea is well-centered and has a definite tinycentral steeper island to support an efficient reduction in myopia andpresbyopia. This case has also been followed for 3 months with no sideeffects.

[0105] It should be appreciated by those skilled in the art that thelenses described for Ortho-K may also be used as bi-focal contactlenses, which can be worn during daytime.

[0106] Although the present invention has been described in connectionwith the preferred embodiments, it will be appreciated by those skilledin the art that modifications can be made and alternatives utilizedwithout departing from the spirit and scope of the present invention.

What is claimed is:
 1. An orthokeratology contact lens for a patient'scornea, comprising: an optical zone (20) having a curvature defined by abase curve (30), said base curve being steeper than a measured curvature(12) of a central portion of said cornea; a plateau zone (22) coupled tosaid optical zone and extending radially therefrom, said plateau zonehaving a curvature defined by a plateau curve (34), said plateau curvebeing flatter than said base curve (30); a fitting zone (24) coupled tosaid plateau zone and extending radially therefrom, said fitting zonehaving a curvature defined by a fitting curve (36), said fitting curvebeing steeper than said plateau curve; an alignment zone (26) coupled tosaid fitting zone and extending radially therefrom, said alignment zonehaving a curvature defined by an alignment curve (38), said alignmentcurve being flatter than said fitting curve; a peripheral zone (28)coupled to said alignment zone and extending radially therefrom, saidperipheral zone having a curvature defined by a peripheral curve (42),said peripheral zone forming an edge lift to act as tear reservoir. 2.An orthokeratology contact lens for a patient's cornea, comprising: anoptical-plateau zone having a positive e-value to form an asphericalcurve which is continuously flatter from its central to its peripheralportions, said central portion of said aspherical curve being steeperthan a measured curvature (12) of a central portion of said cornea; afitting zone (24) coupled to said plateau zone and extending radiallytherefrom, said fitting zone having a curvature defined by a fittingcurve (36), said fitting curve being steeper than an outmost portion ofsaid aspherical curve; an alignment zone (26) coupled to said fittingzone and extending radially therefrom, said alignment zone having acurvature defined by an alignment curve (38), said alignment curve beingflatter than said fitting curve; a peripheral zone (28) coupled to saidalignment zone and extending radially therefrom, said peripheral zonehaving a curvature defined by a peripheral curve (42), said peripheralcurve being flatter than said plateau curve (22) by 0-15 diopters, saidperipheral zone forming an edge lift to act as tear reservoir.
 3. Thecontact lens of claim 1, wherein: said base curve is steeper than saidmeasured curvature by about 1-15 diopters and steeper than said plateaucurve by about 3-30 diopters; said optical zone has a width of about 3-8mm; said a plateau zone has a width of about 0.1-2 mm.
 4. The contactlens of claim 1, wherein: said fitting curve is about 5-30 diopterssteeper than said plateau curve and about 1-25 diopters steeper thansaid alignment curve; said fitting zone has a width of about 0.1-2 mm.5. The contact lens of claim 1, wherein: said alignment curve is about1-30 diopters steeper than said plateau curve.
 6. An orthokeratologycontact lens for a patient's cornea, comprising: an optical zone,comprising an inner optical zone (20 a) and an outer optical zone (21a), said inner optical zone having a curvature defined by an inner curve(30 a), said outer optical zone having a curvature defined by an outercurve (31 a), said inner curve being steeper than said outer curve, saidouter curve being flatter than a measured curvature (12) of a centralportion of said cornea, said inner zone having a width of about 0.5-1.5mm; a fitting zone (24) coupled to said outer optical zone and extendingradially therefrom, said fitting zone having a curvature defined by afitting curve (36), said fitting curve being steeper than said outercurve; an alignment zone (26) coupled to said fitting zone and extendingradially therefrom, said alignment zone having a curvature defined by analignment curve (38), said alignment curve being flatter than saidfitting curve; a peripheral zone (28) coupled to said alignment zone andextending radially therefrom, said peripheral zone having a curvaturedefined by a peripheral curve (42), said peripheral zone forming an edgelift to act as tear reservoir.
 7. The contact lens of claim 6, whereinsaid outer optical zone comprises a plateau zone (22) defined by aplateau curve having a same curvature as said outer curve, said plateauzone extending radially from said outer optical zone to form acontinuous curve with said outer optical zone, said plateau curve being1-4 diopters flatter than said inner curve and being 1-30 dioptersflatter than said measure curvature (12) of said central portion of saidcornea.
 8. The contact lens of claim 7, wherein: said plateau curve isflatter than said measured curvature by about 1-30 diopters and flatterthan said inner optical zone by about 1-4 diopters; said optical zonehas a width of about 3-8 mm; said a plateau zone has a width of about0.1-2 mm.
 9. The contact lens of claim 7, wherein: said fitting curve isabout 5-30 diopters steeper than said plateau curve; said fitting curveis about 1-25 diopters steeper than said alignment curve; said fittingzone has a width of about 0.1-2 mm.
 10. The contact lens of claim 7,wherein: said alignment curve is about 1-30 diopters steeper than saidplateau curve.
 11. The contact lens of claim 6, wherein: said outercurve is flatter than said measured curvature by about 1-30 diopters andflatter than said inner curve by about 1-4 diopters; said optical zonehas a width of about 3-8 mm; said a plateau zone has a width of about0.1-2 mm.
 12. The contact lens of claim 11, wherein: said fitting curveis about 5-30 diopters steeper than said outer curve; said fitting curveis about 1-25 diopters steeper than said alignment curve; said fittingzone has a width of about 0.1-2 mm.
 13. The contact lens of claim 12,wherein: said alignment curve is about 1-30 diopters steeper than saidouter curve.
 14. A contact lens for a patient's cornea, comprising: aninner optical zone (20 b) having a curvature defined by an inner curve(30 b); an outer optical-plateau zone having a positive e-value to forman aspherical curve which is continuously flatter from a junction withsaid inner optical zone to its peripheral portions, said junction ofsaid aspherical curve being one of steeper than or same as a measuredcurvature (12) of a central portion of said cornea; a fitting zone (24)coupled to said plateau zone and extending radially therefrom, saidfitting zone having a curvature defined by a fitting curve (36), saidfitting curve being steeper than an outmost portion of said asphericalcurve; an alignment zone (26) coupled to said fitting zone and extendingradially therefrom, said alignment zone having a curvature defined by analignment curve (38), said alignment curve being flatter than saidfitting curve; a peripheral zone (28) coupled to said alignment zone andextending radially therefrom, said peripheral zone having a curvaturedefined by a peripheral curve (42), said peripheral zone forming an edgelift to act as tear reservoir.
 15. A contact lens for a patient'scornea, comprising: an optical zone, comprising an inner optical zone(20 b) and an outer optical zone (21 b), said inner optical zone havinga curvature defined by an inner curve (30 b), said outer optical zonehaving a curvature defined by an outer curve (31 b), said inner curvebeing steeper than said outer curve, said outer curve being steeper thana measured curvature (12) of a central portion of said cornea, saidinner zone having a width of about 0.5-1.5 mm, said outer zone having awidth of about 1-4 mm; a plateau zone (22) coupled to said outer opticalzone and extending radially therefrom, said plateau zone having acurvature defined by a plateau curve (34), said plateau curve beingflatter than said inner curve and said outer curve; a fitting zone (24)coupled to said plateau zone and extending radially therefrom, saidfitting zone having a curvature defined by a fitting curve (36), saidfitting curve being steeper than said plateau curve; an alignment zone(26) coupled to said fitting zone and extending radially therefrom, saidalignment zone having a curvature defined by an alignment curve (38),said alignment curve being flatter than said fitting curve, saidalignment curve being steeper than said plateau curve; a peripheral zone(28), coupled to said alignment zone and extending radially therefrom,said peripheral zone having a curvature defined by a peripheral curve(42), forming an edge lift as tear reservoir.
 16. The contact lens ofclaim 15, wherein said plateau zone is merged with said outer opticalzone by positive e-value to form a continuously flatter aspheric curve.17. The contact lens of claim 15, wherein: said fitting curve is 5-30 Dsteeper than said plateau curve; said fitting curve is 1-25 D steeperthan said alignment curve; said fitting zone has a width of about 0.1-2mm.
 18. The contact lens of claim 15, wherein: said alignment curve is1-30 D steeper than said plateau curve.
 19. The contact lens of claim15, wherein said peripheral curve is 0-15 flatter than said plateaucurve.
 20. The contact lens of claim 15, wherein: said outer opticalzone is steeper than said measured curvature by about 1-15 diopters, andis flatter than said inner optical zone by about 1-4 diopters; saidouter optical zone has a width of about 1-4 mm; said outer optical zoneis steeper than said plateau zone by about 3-30 diopters; said plateauzone has a width of about 0.1-2 mm.